Reaction Order Research Articles

Chemoenzymatic synthesis of 7-chloro-4-Dimethylallyl-L-Tryptophan, a fragment of krisynomycin

The krisynomycins are macrocyclic depsipeptide natural products from Streptomyces that act as imipenem potentiators against methicillin-resistant Staphylococcus aureus (MRSA). The flagship molecule of this family, krisynomycin, features a unique 7-chloro-4-dimethylallyl-l-tryptophan (7-Cl-4-Pren-Trp) fragment that is both essential for biological activity and unprecedented among bacterial natural products. In silico analysis of the putative biosynthetic gene cluster revealed an aromatic prenyltransferase and a tryptophan halogenase, though the precise reaction order en route to 7-Cl-4-Pren-Trp remained ambiguous. We report herein a brief chemoenzymatic synthesis of 7-Cl-4-Pren-Trp through a prenylation-chlorination sequence, which contains the first ever C4 prenylation of tryptophan by a bacterial enzyme. Furthermore, our efforts provide tentative evidence that the same reaction sequence is operative in the biosynthesis of krisynomycin.

Comprehensive batch studies on removal of fluoride from aqueous solution by acid and alkali-activated adsorbents prepared from Dal lake weeds: Mechanism, Kinetics and Thermodynamics

An efficient and economical way of eliminating fluoride from water is being investigated by employing the buoyant aquatic plant (Dal weed). Two post-pyrolysis chemical activation alteration techniques were implemented: acidic activation by employing sulfuric acid (H-activation) and alkaline activation using sodium hydroxide (OH-activation). The batch kinetic studies have been carried out considering varying starting fluoride levels such as 2–10 mg/L. The impact of diverse procedural factors, including dosage of Dal weed, starting fluoride level, pH and contact duration was observed to determine their influence on fluoride adsorption kinetics. Based on analyzed exploratory results, removal efficacy of 63% for the OH-activated carbon and 83% for H-activated carbon was achieved at commencing fluoride level of 10 mg/L, adsorbent dosage of 0.8 g, at 25 °C after 120 min. The maximal fluoride uptake capacity for H-activated carbon was observed to be 78.158 mg/g. Kinetic investigations showed that the Freundlich isotherm model provided a satisfactory match with an R2 value of 0.99. The reaction order nature adhered to kinetics resembling pseudo second order. Thermodynamic investigation revealed endothermic sorption, with negative ΔG indicating spontaneous fluoride uptake. In comparison, the positive number for ΔS suggested random behavior at the contact involving the adsorbent and adsorbate. The investigations into the regeneration capabilities of the adsorbent material revealed that even after undergoing for five consecutive cycles of adsorption and regeneration, the adsorbent exhibited an uptake potential of 45%. The presence of competing ions in the solution negatively impacted defluoridation efficacy, with the influence following the order of HCO3−< NO3−< Cl−< SO42−< PO43−.

Selective Recovery of Tin from Electronic Waste Materials Completed with Carbothermic Reduction of Tin (IV) Oxide with Sodium Sulfite

A new approach for the thermal reduction of tin dioxide (SnO2) in the carbon/sodium sulfite (Na2SO3) system is demonstrated. The process of tin smelting was experimentally optimized by adjusting the smelting temperature and amounts of the chemical components used for the thermal reduction of SnO2. The numbers obtained are consistent with the thermodynamic characteristics of the system and molar fractions of reactants derived from the proposed mechanism of the SnO2 thermal reduction process. They reveal that the maximum yield of tin is obtained if masses of C, Na2SO3 and SnO2 are approximately in the ratio 1:2:3 and the temperature is set to 1050 °C. The key role in the suggested mechanism is the thermal decomposition of Na2SO3. It was deduced from the available experimental data that the produced sulfur dioxide undergoes carbothermic reduction to carbonyl sulfide—an intermediate product involved in the bulk reduction of SnO2. Replacing sodium sulfite with sodium sulfate, sodium sulfide and even elemental sulfur practically terminated the production of metallic tin. The kinetic analysis was focused on the determination of the reaction orders for the two crucial reactants involved in the smelting process.

The K346T mutant of GnT-III bearing weak in vitro and potent intracellular activity

BackgroundN-Acetylglucosaminyltransferase-III (GnT-III, also designated MGAT3) catalyzes the formation of a specific N-glycan branch, bisecting GlcNAc, in the Golgi apparatus. Bisecting GlcNAc is a key residue that suppresses N-glycan maturation and is associated with the pathogenesis of cancer and Alzheimer's disease. However, it remains unclear how GnT-III recognizes its substrates and how GnT-III activity is regulated in cells. MethodsUsing AlphaFold2 and structural comparisons, we predicted the key amino acid residues in GnT-III that interact with substrates in the catalytic pocket. We also performed in vitro activity assay, lectin blotting analysis and N-glycomic analysis using point mutants to assess their activity. ResultsOur data suggested that E320 of human GnT-III is the catalytic center. More interestingly, we found a unique mutant, K346T, that exhibited lower in vitro activity and higher intracellular activity than wild-type GnT-III. The enzyme assays using various substrates showed that the substrate specificity of K346T was unchanged, whereas cycloheximide chase experiments revealed that the K346T mutant has a slightly shorter half-life, suggesting that the mutant is unstable possibly due to a partial misfolding. Furthermore, TurboID-based proximity labeling showed that the localization of the K346T mutant is shifted slightly to the cis side of the Golgi, probably allowing for prior action to competing galactosyltransferases. ConclusionsThe slight difference in K346T localization may be responsible for the higher biosynthetic activity despite the reduced activity. General significanceOur findings underscore the importance of fine intra-Golgi localization and reaction orders of glycosyltransferases for the biosynthesis of complex glycan structures in cells.

Efficient recovery of highly pure CaF2 from fluorine-containing wastewater using an icy lime solution.

Developing a feasible and low-cost strategy for the recovery of calcium fluoride efficiently from fluoride-containing wastewater is very essential for the recycle of fluoride resources. Herein, a modified lime precipitation method was employed to recover CaF2 from fluorinated wastewater using a special icy lime solution. Intriguingly, the highest F- removal was greater than 95% under the optimal condition, leaving a fluoride concentration from 200 to 8.64 mg/L, while the lime dosage was much lower than that of industry. Importantly, spherical-shaped CaF2 particles with a 93.47% purity and size smaller than 600 nm were recovered, which has a high potential for the production of hydrofluoric acid. Besides, the precipitation was significantly affected by Ca/F molar ratio, stirring time, temperature, and solution pH. Furthermore, the thermodynamics and kinetics were investigated in detail to reveal the crystallization process. As a result, the defluorination reaction followed the pseudo-second order reaction kinetics model. Also, CO2 in the air adversely influenced the CaF2 purity. Based on this facile method, a high lime utilization efficiency was applied to defluorination, which contributed to protecting the environment and saving costs. This study, therefore, provides a feasible approach for the green recovery of fluorine resources and has significance for related research.

Kinetic study of magnesium dissolution using a magnesium oxide industrial by-product

Phosphorus recovery via struvite precipitation in wastewater treatment plants (WWTPs) is a key technology for nutrient recovery. This work investigates the dissolution kinetics of an industrial low-grade magnesium oxide (LG-MgO) by-product as an alternative to common magnesium sources for struvite precipitation. The main aims were to develop a parsimonious dissolution kinetic model capable of predicting the release of magnesium into the solution with accuracy and studying the influence of temperature on dissolution kinetics. The simultaneous fitting of all the experiments by non-linear regression rendered overall process values of the dissolution model’s frequency factor (498,606 L3.22 min−1 mmol−1.74), activation energy (37.51 kJ·mol−1), and reaction order (2.74). The goodness-of-fit for all experiments was evaluated by the total sum of squared residuals and R2 coefficients, being excellent under all conditions. The estimated kinetic coefficient values showed a temperature-dependent variation of the kinetic coefficient, increasing from 0.079 to 0.219 L3.22 min−1 mmol−1.74 when the temperature increased from 15 to 35 °C. The magnesium dissolution was fast in the first 5 min, where 40–78 % of magnesium dissolved with respect to the initial magnesium in the solid. Despite the assumptions made in the model derivation, the developed kinetic model provides a practical, reliable, and easy-to-use tool for WWTPs to estimate the LG-MgO dosage required to achieve targeted magnesium concentrations, thereby improving reagent use efficiency and phosphorus recovery.

Solubility, pH-Solubility Profile, pH-Rate Profile, and Kinetic Stability of the Tyrosine Kinase Inhibitor, Alectinib.

Alectinib HCl (ALBHCl) is a tyrosine kinase inhibitor used for non-small cell lung carcinoma (NSCLC). The aim of this study is to unlock some of the physicochemical properties of ALBHCL that serve as a database for any future studies. A solubility study of ALBHCL was performed in different solvents. Also, photostability was tested in the solution and solid states, and the order of reaction and rate constant were calculated. In addition to the pH solubility relation, the pH-rate relation at different temperatures was also studied, and the profiles were constructed. A solubility study was also performed in different media for the purpose of optimizing suitable sink conditions for the in vitro dissolution testing of solid dosage forms. Solubility tests in multiple solvents and pH conditions revealed that the highest solubility was in DMSO, methanol, and chloroform, with acidic media yielding the maximum solubility but degrading at rather low pH levels. ALBHCL proved unstable at high temperatures and under light exposure, with varying stability across different pH levels. The optimal dissolution media for in vitro oral dosage form evaluation were determined, achieving sink conditions at pH levels of 6.8 and 4.5 with specific additives. This study enhances the existing database on ALBHCL's physicochemical properties, emphasizing the importance of pH optimization in pharmaceutical processes and providing valuable insights into its pharmaceutical application.

Experimental and theoretical quantum chemical studies of 2-(2-acetamidophenyl)-2-oxo-N-(pyridin-2-ylmethyl)acetamide and its copper(II) complex: molecular docking simulation of the designed coordinated ligand with insulin-like growth factor-1 receptor (IGF-1R)

Newly synthesized ligand 2-(2- acetamidophenyl)-2-oxo-N-(pyridin-2-ylmethyl)acetamide and its copper(II) complex were characterized by elemental analyses, FT-IR, UV–Vis., ESR, 1H-NMR, and thermal analysis along with the theoretical quantum chemical studies. Combined experimental and theoretical DFT (density functional theory) studies showed the ligand to be a tridentate ligand with three coordinate bonds. The complex was suggested to be in a distorted octahedral structure with dx2-y2 ground state. The activation energy, ΔE*; entropy ΔS*; enthalpy ΔH* and order of reaction has been derived from differential thermogravimetric (DTA) curve, using Horowitz–Metzeger method. The nujol mull electronic spectrum of the ligand and Cu(II) complex have been recorded and the difference of the excited and ground state densities has also been theoretically calculated and plotted to investigate the movement of electrons on excitation. The Cu(II) complex was evaluated for its antibacterial activity against two bacterial species, namely Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Antifungal screening was performed against two species (Condida albicans and Aspergillus flavus). The complex under investigation was found to possess notable biological activity. Molecular docking investigation predicted different types of non-covalent interactions of the synthesized ligand towards Insulin-like growth factor 1 receptor (ID: 5FXR).

Determination of output composition in reaction-advection-diffusion systems on network reactors

We consider reaction-transport processes in open reactors in which systems of first order reactions involving a number of gas species and solid catalysts can occur at localized active regions. Reaction products flow out of the reactor into vacuum conditions and are collected at an exit boundary. The output composition problem (OCP) is to determine the composition (molar fractions) of the collected gas after the reactor is fully emptied. We provide a solution to this problem in the form of a boundary-value problem for a system of time-independent partial differential equations. We then consider network-like reactors, which can be approximated by a network consisting of a collection of nodes and 1-dimensional branches, with reactions taking place at nodes. For these, the OCP can be solved in a simple and effective way, giving explicit formulas for the output composition as a function of the reaction coefficients and parameters associated with the geometric configuration of the system. The possibility of determining reaction coefficients from experimentally obtained output composition is shown in the case of one chemically active node.

Sono-photocatalytic degradation of Tetracycline and Ciprofloxacin antibiotics using microwave-reflux of NiO-MoS2/rGO ternary nanocomposite

In this study, NiO-MoS2/rGO nanocomposites were synthesized successfully by a simple microwave assisted refluxing method by varying the mass ratios of rGO. The NiMG-50 ternary nanocomposite has been applied by sonocatalytic, photocatalytic and sono-photocatalytic degradation for the removal of tetracycline (TTC) and ciprofloxacin (CIP) antibiotics. Physicochemical properties of the synthesized samples were characterized by Powder X-ray Diffraction (PXRD), Energy Dispersive X-ray Spectroscopy (EDAX) and X-ray Photoelectron Spectroscopy (XPS) corroborated the phase purity of NiMG-50 nanocomposite. The High Resolution Scanning Electron Microscopy (HR-SEM) image reveals the zigzag arrangements of NiO nanoflakes over MoS2 and rGO sheets. The tight contact of platelet shaped-NiO NP’s and curled layer-MoS2 on the sheets of rGO results in the separation of photo-induced e--h+ pairs as demonstrated by the High Resolution Transmission Electron Microscopy (HR-TEM) analysis. Optical properties reveal a reduced band gap and enhanced separation efficiency with fast charge transfer rate, improving the organic pollutant degradation efficiency. NiMG-50 demonstrated a good catalytic activity against TTC and CIP in sono-photocatalytic process with an efficiency of 94.10 % and 83.96 % at 35 and 90 min, respectively. Simultaneously, the experimental results showed that the NiMG-50 composite follows the pseudo-first order reaction kinetics with a rate constant (KSP) value of 0.077 min−1 and 0.015 min−1 for TTC and CIP. The radical trapping test and degradation mechanism indicated that the continuous contribution of ̇OH and ̇O2– reactive radicals are the major ones responsible for the active involvement in the degradation reaction. This research work gives a fresh prospects to the as prepared NiMG catalyst as an efficient composite with a good applicability for the sono-photocatalytic degradation of pharmaceutical products.

Preparation of thiourea derivative incorporated Ag3PO4 core shell for enhancement of photocatalytic degradation performance of organic dye under visible radiation light

Photocatalysis is a promising technique to reduce hazardous organic pollutants using semiconductors under visible light. However, previous studies have been concerned with the behavior of silver phosphate (Ag3PO4) as n-type semiconductors, and the problem of their instability is still under investigation. Herein, 4,4′-(((oxalylbis(azanediyl)) bis(carbonothioyl)) bis(azanediyl)) dibenzoic acid is synthesized by green method and used to enhance the photocatalytic behavior for Ag3PO4. The incorporated Ag3PO4 core–shell is prepared and characterized via XRD, FT-IR, Raman, TEM and BET. Besides, the thermal stability of the prepared core shell was investigated via TGA and DSC measurements. The optical properties and the energy band gap are determined using photoluminescence and DRS measurements. The photodegradation of methylene blue in the presence of the synthesized Ag3PO4 core–shell under visible light is examined using UV/Vis measurements. The effect of initial dye concentration and contact time are studied. In addition, the kinetic behavior of the selected dye during the photodegradation process shows a pseudo-first order reaction with rate constant of 0.015 min−1 for ZAg. The reusability of the Ag3PO4 core shell is evaluated, and the efficiency changed from 96.76 to 94.02% after three cycles, indicating efficient photocatalytic behavior with excellent stability.

Physical limits to acceleration of enzymatic reactions inside phase-separated compartments.

We present a theoretical analysis of phase-separated compartments to facilitate enzymatic chemical reactions. While phase separation can facilitate reactions by increasing local concentration, it can also hinder the mobility of reactants. In particular, we find that the attractive interactions that concentrate reactants within the dense phase can inhibit reactions by lowering the mobility of the reactants. This mobility loss severely limits the potential to enhance reaction rates. Phase separation provides greater benefit in situations where multiple sequential reactions occur and/or high order reactions, provided the enzymes are unsaturated, transport to the condensate is not limiting, and the reactants are mobile. We show that mobility can be maintained if recruitment to the condensed phase is driven by multiple attractive moieties that can bind and release independently. However, the spacers necessary to ensure independence between stickers are prone to entangle with the dense phase scaffold. We find an optimal sticker affinity that balances the need for rapid binding/unbinding kinetics and minimal entanglement. Reaction rates can be accelerated by shrinking the size of the dense phase with a corresponding increase in the number of stickers. Our results showcase the potential capabilities of phase-separated compartments to act as biochemical reaction crucibles within living cells.

Enhancement of Heat and Mass Transfer in 2D-Mixed Convection Nano-Liquid Flow Over a Flexible Riga Plate with Heat Source/Sink and Chemical Reaction

This study delves into the complex dynamics of two-dimensional (2D) hydro-magnetic nano-fluidic flow over an elastic Riga plate, aiming to elucidate the interactions among thermal energy, concentration transfer, pressure gradient, and convective &amp; zero mass flux at the boundary. Notably, the investigation incorporates concentration and temperature buoyancy forces, integrating them into the analysis with a comprehensive energy transfer equation and essential nanofluid properties in the species concentration. Further, the internal heat source/sink and rate of first order chemical reaction are considered. Employing the advanced capabilities of MATHEMATICA12 software, the study applies the Optimal Homotopy Analysis Method (OHAM), reducing the governing equations partially to ordinary ones. Furthermore, the study reveals intriguing patterns, highlighting the significant impact of the modified Hartmann number on velocity and concentration gradients, while displaying contrasting effects on thermal profiles. Moreover, the dual nature of pressure gradient behavior underscores the complexity of the studied phenomenon, offering valuable insights for further research and practical applications in nano-fluidic systems.

КІНЕТИКА КОМПЛЕКСОУТВОРЕННЯ 2-МЕТОКСИФЕНОЛУ З ЙОНОМ ФЕРУМУ (III) ТА ЙОНОМ ГЕКСАЦІАНОФЕРУМУ (III)

Study of the formation of complexes of 2-methoxyphenol with ferrum (III) ion or hexacyanoferrum (III) ion. Kinetic studies have shown that the order of reaction for ferrum ion or ferrum hexacyanoion is close to one. The order of reaction for 2-methoxyphenol is 0.8 in the reaction with ferrum (III) ion and close to zero in the reaction with ferrum (III) hexacyanoion. It has been shown that the formed complexes are stable in acidic solution at pH less than 7 and rapidly decompose in alkaline solution. The complex of iron ion with 2-methoxyphenol decomposes into 2-methoxyphenol and ferrum hydroxide at pH above 8. At the same time, the rapid oxidation of 2-methoxyphenol is observed with increasing pH of the solution of the hexacyanoiron ion complex with 2-methoxyphenol. The found Kp values for the interaction of ferrum ion with 2-methoxyphenol are much higher than for the reaction with hexacyanoferrum ion.

Reaction order of near equilibrium calcite dissolution: Uncertainties and ambiguities of isotopic tracer methods

Dissolution of calcite in water is fundamental to geochemistry. Laboratory methods generally give consistent dissolution rates under conditions far from equilibrium, but close to equilibrium the measurement of dissolution using isotopes is complicated by poorly understood calcite-fluid isotopic exchange processes. This near-equilibrium isotopic exchange occurs in laboratory experiments at rates of order 10-9 to 10-13 mol/m2/s and decreases with experiment duration approximately as 1/time where time is measured from the start of the experiment. Such rates are fast enough to compete with dissolution in days-long experiments and consequently, net dissolution rates may not be measurable with isotopic tracer methods except in experiments carried out for long enough to allow the background exchange to dissipate sufficiently. To better define what should be expected for isotopic signals during dissolution, we develop a quasi-1D model for calcite dissolution that includes the mechanistically unconstrained isotopic exchange as well as solid state diffusion. We use the model, the observations reported in the literature, and the calcite dissolution rates in seawater reported by Naviaux et al., (2019a) to illustrate ambiguities in measurement of near-equilibrium calcite dissolution rates. The results suggest that the reaction order of calcite dissolution close to equilibrium could be 2 at both room temperature and the lower temperatures of the seafloor. The reaction order of near-equilibrium calcite dissolution is important for understanding calcite mineral surface processes, long-term behavior of dissolution on the seafloor, and alkalinity fluxes from modern seafloor sediments. Distinguishing between net dissolution, which affects fluid saturation state, and “exchange,” which doesn’t, is important but typically cannot be done with isotopic tracers alone.

Unlocking the Power of Solar Synergy: Enhanced Nitrophenol Degradation using ADGCAAQ Photocatalyst

The remarkable mechanical and chemical characteristics of graphene have garnered significant interest in scientific investigations aimed at addressing severe environmental problems and energy shortages. A concerning problem is the careless disposal of industrial wastes that contain a variety of organic contaminants in water bodies. In order to create the ADGCAAQ light harvesting photocatalyst, a simple and extremely effective condensation process involving 1, 4-diamino anthraquinone (AAQ) and graphene generated from aloe vera (ADG) has been urbanized. Several approaches are used to analyze the newly constructed photocatalyst, indicating that it has the requisite potential to degrade 4-nitrophenol. By analyzing the degradation rate and order reaction of the degradation process, the kinetics of the degradation route have been used to analyze the mechanistic pathway for the degradation of 4-nitrophenol using a reducing agent and the ADGCAAQ photocatalyst. Under outside solar spectrum conditions, the photocatalytic activity of ADGCAAQ photocatalyst tested with 4-nitrophenol shows significant degradation efficiency with reducing agent H2O2.

Hydrogenation features of TiZrHfNbTa high-entropy alloy produced by calcium-hydride synthesis

A high-entropy alloy TiZrHfNbTa has been synthesized by a method of the mutual reduction of the higher oxides of corresponding metals with calcium hydride. The alloy structure was characterized and hydrogen absorption properties were studied. The alloy of overall equiatomic composition TiZrHfNbTa consists of two BCC phases with unit cell parameters of 3.419 and 3.328 Å. The distribution of the elements was established as follows: Ti0.21Zr0.24Hf0.24Nb0.25Ta0.06 (BCC-I) and Ti0.15Zr0.05Hf0.10Nb0.08Ta0.62 (BCC-II). The hydrogenation behavior of the alloy under different conditions was thoroughly studied. It was shown that complete hydrogenation resulted in the formation of FCC-type (H/M → 2) and BCT-type hydrides (H/M → 1) from BCC-I and BCC-II, respectively. Under low hydrogen pressure (< 212.8 Torr), BCC-I absorbed up to 0.33 at. H/M within a solid solution without changing the structural type. According the kinetic analysis, this process can be described as a second order reaction with activation energy of 102 kJ/mol. The BCC-I-based solid solution is capable of retaining hydrogen in a deep vacuum at a temperature of 430 °C. The fast kinetics of hydrogen absorption and high thermal stability allow us to suggest the studied two-phase TiZrHfNbTa alloy as a promising getter for vacuum devices.

A study of electro-magneto Darcy-Forchheimer Casson nanofluid flow under the effects of Cattaneo-Christov double diffusive model over linear vs nonlinear stretching sheets

The present study reveals that the two-dimensional incompressible Casson nanofluid saturated the porous media in the presence of Darcy-Forchheimer medium over a non-linear sheet stretching. It has immense practical applications in engineering, like paper production, solar receivers, aluminous plate cooling, plastic sheet extrusions, petroleum resources, soil physics, etc. Here, non-linear stretching is supposed to be the driving force. The electro-magnetized Cattaneo-Christov double diffusion model was imposed to enhance the heat and mass transfer along with the influences of ist order chemical reactions, Brownian diffusion, thermophoresis motion, internal heat source viscous-ohmic dissipation, and thermal radiation. The electro-magnetic impacts are uniformly normal to the direction of flow. The governing flow model, a system of highly coupled and non-linear partial differential equations, is converted into ordinary differential equations imposing appropriate similarity transformations, and solved analytically (differential transformation method via MAPLE) and numerically (Bvp4c via MATLAB). The final results are tabulated and demonstrated graphically for different control parameters. In addition, the contour graphs have been prepared. For engineering and industrial importance, a significant difference can be observed in the enhancement of heat and mass transfer through temperature and concentration profiles and tables of Nusselt as well as Sherwood numbers. Through histograms, it is concluded that the nonlinear stretching sheet provides a better heat and mass transfer rate as compared to the linear stretching sheet. The rate of heat transfer in the linear vs nonlinear stretching sheet is 25–75%, but the rate of mass transfer is 30–70%.

Recyclable Ag-Au bimetallic nanoparticles supported on acid functionalized multi walled carbon nanotubes for effective catalytic applications

In the present investigation, in situ green reduction approach is used to uniformly decorate the Ag-Au bimetallic nanoparticles (BNPs) on the surface of acid functionalised multi-walled carbon nanotubes (MWCNTs). The adsorbed Terminalia catappa aqueous leaf extract biopolymers on the surface of MWCNTs can increase the in situ reduction of Ag, Au ions to Ag-Au BNPs and stabilise them which can operate as a capper/stabiliser and reductant agent. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy - energy dispersive x-ray spectroscopy (SEM-EDX), Fourier-transform infrared spectroscopy (FT-IR) and UV–visible spectroscopy techniques were employed to examine the structures, morphologies, composition, chemical bonds and optical properties of the functionalised MWCNTs and the nanohybrid. The results revealed that the spherical T.C-Ag-Au bimetallic nanoparticle with average size 12.4 nm was uniformly distributed on the surface of modified MWCNTs. Finally, evaluation of the catalytic activity of the T.C-Ag-Au BNPs decorated MWCNTs exhibited excellent catalytic performance for completing the reduction of 4-Nitrophenol (4-NP) and degradation of alizarin red (AR) dye at ambient temperature with a great rate constant and the degradation efficiency of 98.7% and 96.4%, respectively. The order of reaction, rate constant, half-life and mechanism of catalytic activity of the T.C-Ag-Au BNPs@COOH-MWCNTs nanohybrid were calculated using the Langmuir–Hinshelwood model. The catalyst can be retained and reapplied eight times without affecting its catalytic performance. The interaction between T.C-Ag-Au BNPs and MWCNTs has a synergistic effect, which is accountable for the enhanced catalytic activity.

Thermal Decomposition Mechanism of P(DAC-AM) with Serial Cationicity and Intrinsic Viscosity.

The thermal decomposition of the thermodynamic, kinetic and mechanisms of copolymer P(DAC-AM) samples with serial cationicity and intrinsic viscosity ([η]), and the control samples of homopolymer PAM and PDAC, were studied and analyzed using TG, DSC, FTIR. The results of the thermal decomposition thermodynamics confirmed that the thermal decomposition processes of the serial P(DAC-AM) samples and the two control samples could be divided into two stages. It was found that the processes of the copolymer P(DAC-AM) samples were not a simple superposition of those of homopolymers, whose monomers had composed the unit structures of the copolymer, but there were interactions between the two suspension groups. The results of thermal decomposition kinetics showed that the apparent activation energy (E) of the thermal decomposition process of all polymer samples had different varying trends in the terms of weight-loss rate (α). The reaction order (n) of the thermal decomposition of P(DAC-AM) in Stage I and II was close to 1, but in the former and the latter it tended to be 2 and 0.5, respectively. Finally, the thermal decomposition mechanism of copolymer P(DAC-AM) samples was discussed. The above research could not only fill in the knowledge vacancy of the thermal decomposition of the thermodynamic, kinetic and mechanisms of P(DAC-AM), but could also lay a foundation for the study of thermal decomposition mechanisms of the other types of polymers, including cationic polymers.